Car Won't Start

[kygaca]

Needed a new gas tank so I installed that along with a new fuel pump. Now the car won't start! So I checked wiring at the back of the car and the wire going to the pump has 0 volts, the sender only has 8 volts. Went under the car trying to find anything wrong with the wiring, maybe some shoddy connections from previous owners but seems solid. My next thought process is a fuel pump relay. Chevy doesn't make this part anymore and I can't find it. Is there a way to bypass this and maybe get my car running again?

 

[pontiacgp]

what car do you have to have a stock in tank pump?

 

[kygaca]

It is an 87 El Camino with a 4.3L engine. I went to a junkyard yesterday and tried to find it - they had one el camino and someone already took it. Checked Caprices, some trucks and still couldn't find it.

 

[fleming442]

Get one of these
https://www.amazon.com/dp/B00FOVNNL8/?tag=gbody-20

The bottom of the GM relay should have terminal numbers; they're universal, so just match them up.

Have you confirmed power to the suspect relay? Should have ignition on on 2 terminals, ground on one, and the 4th to the pump.

 

[kygaca]

fleming442 , I installed the relay you suggested, followed the wiring diagram and I am pretty sure I got it wired correctly. That didn't solve it but I did some more research and got a new Oil Pressure Switch. I can now hear the fuel pump! Before I couldn't, so I feel as though I am getting closer, (although I can't hear the fuel pump prime until AFTER I crank it). Went to auto zone and got some starting fluid and it starts right up. I am clueless, any help would be appreciated guys.

 

[fleming442]

I've heard that some models have the fuel pump relay tied to the oil pressure switch. That's how you do it with aftermarket electric pumps, too. The theory is that the engine shouldn't be allowed to run if there's no oil pressure.

 

[64nailhead]

Needed a new gas tank so I installed that along with a new fuel pump. Now the car won't start!

If it ran before you swapped the tank and pump, then you probably can stop looking under the hood with the exception of the fuel pump fuse. But if you must, then check the relay wiring to confirm all is well. Then jump pin 30 to 87 with a paperclip and see if the pump runs. If you have power at pin 30 that will light head light bulb and the pump doesn't run when jumped from 30 to 87, then you have a wiring issue from the relay to the pump.

When in doubt, run another wire to the pump supplied voltage from the same wire that runs the coil so that it will be hot in crank and run. Then determine the root cause of your wiring issue.

Obviously, if the pump doesn't run when powered at the pump plug, then you have a bad pump or ground at the pump.

 

[kygaca]

64nailhead I just jumped 30 to 87 and the pump definitely is running.

 

[64nailhead]

That's great. So now you need a wiring diagram for your motor/car. Fleming had you going in the right direction. If I had one for an ECM car, then I'd check it out for you.

In a nutshell, either pin 85 or 86 will have 12 volts with the key on or all the time. Whichever pin doesn't have 12 volts should have a ground when the engine is cranking. Checking for ground is a pain without a something like a Power Probe. But a wiring diagram is the first place to check. There is an EXCELLENT chance that ether the power or ground runs through the oil pressure sensor. But I can't tell without a diagram.

So, is it safe to say that this ran before you swapped the tank and pump? If yes, then it should run unless you somehow popped a fuse for ???? something.

 

[fleming442]

There's also the fact that the battery needs to have enough @$$ to spin the engine over fast enough to create said oil pressure to close said switch. If you just want to get it running, ground the oil pressure wire on the fuel pump relay.